In recent years, the improvement in portability and operability has been demanded for the image-pickup apparatus such as a digital still camera and a digital video camera. The whole camera is now required to be small-sized and the miniaturization of an optical system such as a lens and a lens barrel employed in the image-pickup apparatus has been in progress. In addition, a further enhancement of image-quality and pixels of taken pictures is also strongly requested and lenses forming an optical system may be made large in size; however, the miniaturization of the optical lens barrel is often demanded by making a drive mechanism smaller in size.
There are similar demands with respect to what is called a collapsible lens used in the image-pickup apparatus such as a digital still camera and a digital video camera, and the miniaturization, thin-making and the like are requested in view of convenience for portability.
FIG. 3 shows a state in which, for example, a digital still camera provided with a collapsible type lens is not used and the lens is retracted, that is, shows an outer appearance perspective view of the retracted position of the lens. FIG. 4 shows a state in which a digital camera is used and the lens barrel is extended, that is, shows an outer appearance perspective view of a wide angle position or a telephoto position of the same camera.
FIGS. 5A, 5B and 5C show sectional views of a conventional collapsible lens. FIG. 5A shows a section of the lens in the retracted position when not in use; FIG. 5B shows a section of the wide angle position; FIG. 5C shows a section of the telephoto position. FIG. 6 shows an exploded perspective view of the collapsible lens.
First, main functions of a digital still camera will be described with reference to FIGS. 3 and 4. A reference numeral 1 denotes a camera body of the digital still camera and a reference numeral 2 denotes an image-pickup lens portion of a collapsible type, which is provided on one side of the front surface of the camera body 1. In the collapsed state shown in FIG. 3, barriers 3 protect the front lens surface of the image-pickup lens portion 2. Further, on the front surface of the camera body 1 are arranged a finder lens 4, a strobe 5, and an autofocus-auxiliary-light receiving portion 6 for detecting a distance to a subject. Further, a reference numeral 7 denotes a finder window, a numeral 8 denotes a shutter button, and a numeral 9 denotes a knob for changing the mode.
Next, the structure of the image-pickup lens portion 2 that is a collapsible type optical unit will be described in detail with reference to FIGS. 5A, 5B, 5C and FIG. 6.
A reference numeral 10 denotes a first group lens frame holding a plurality of lenses 11. The first group lens frame 10 includes a plurality of cam pins 10a to be fitted into a first cam groove 12a of a cam ring 12. The first group lens frame 10 is formed of, for example, black polycarbonate resin containing glass fiber and has the strength and a light shielding nature.
A reference numeral 13 denotes a second group lens frame holding a plurality of lenses 13a. The second group lens frame 13 includes a plurality of cam pins 13b to be fitted into a second cam groove 12b of the cam ring 12. The second group lens frame 13 is formed of, for example, black polycarbonate resin containing glass fiber and has the strength and a shielding nature. The second group lens frame 13 may be provided with an iris shutter mechanism.
The above-described cam ring 12 includes a gear portion 12c to be driven to rotate within the internal circumference of a fixed ring 15 by means of a gear 14a of a gear unit 14, and a plurality of cam pins 12d to be fitted into a cam groove 15a of the fixed ring 15. The cam ring 12 is formed of, for example, black polycarbonate resin containing glass fiber, and has the strength and a light shielding nature. By means of the first cam groove 12a and the second cam groove 12b, a zooming operation is performed in which the first group lens frame 10 and the second group lens frame 13 are moved along the predetermined curve in the direction of the optical axis L.
A reference numeral 16 denotes a straight-forward guide ring which is a member that moves within the internal circumference of the fixed ring 15 integrally with the cam ring 12 in the direction of the optical axis L. The straight-forward guide ring 16 includes a plurality of guide grooves 16a which guides the first group lens frame 10 in the direction of the optical axis and a plurality of guide grooves 16b which guide the second group lens frame 13 in the direction of the optical axis. The straight-forward guide ring 16 is formed of, for example, black polycarbonate resin containing glass fiber and has the strength and a light shielding nature.
The fixed ring 15 is a member fixed to a rear barrel 17. The fixed ring 15 is formed of, for example, black polycarbonate resin containing glass fiber and has the strength and a light shielding nature.
A reference numeral 18 denotes a third group lens frame holding a lens 19. The third group lens frame 18 is formed of, for example, black polycarbonate resin containing glass fiber and has the strength and a light shielding nature. The third group lens frame 18 is retained so as to be movable in the direction of the optical axis with respect to the rear barrel 17, which is designed to displace minutely in the direction of the optical axis by means of a power source such as a stepping motor (not shown).
To the rear barrel 17 are fixed the fixed ring 15, a barrier drive mechanism 20, and the gear unit 14. Further, to the rear barrel 17 is fixed an optical filter 22 composed of an optical low-pass filter or an infrared cut filter at a holding portion 21 facing the third group lens frame 18 so as to be positioned by an elastically-forced sealing rubber 23. Furthermore, to the rear barrel 17 is fixed a solid-state image-pickup device 24 such as CCD and CMOS positioned behind the optical filter 22.
The barrier drive mechanism 20 is a projection member for driving to close barriers 3 linked with the collapsing operation of the image-pickup portion 2. The gear unit 14 drives to rotate the cam ring 12 through the gear portion 12c engaged with the gear 14a; and the gear ratio is determined such that a sufficient driving power in the range of collapsed state to wide state to telephoto state, and telephoto state to wide state to collapsed state.
Next, the operation of the above-described image-pickup lens portion 2 will be described.
In operation from the collapsed state in FIG. 5A to the wide position in FIG. 5B, the gear 14a of the gear unit 14 is driven by a driving source such as a DC motor, the gear portion 12c being rotated, the cam pin 12d being rotated along the cam groove 15a of the fixed ring 15, and the cam ring 12 being moved toward a subject in the direction of the optical axis. At this moment, the straight-forward guide ring 16 moves forward integrally with the cam ring 12 as shown by an arrow mark A.
At the same time, the cam pin 10a is moved along the first cam groove 12a of the cam ring 12 and the guide groove 16a of the straight-forward guide ring 16 with the result that the first group lens frame 10 is moved forward as shown by an arrow mark B. Concurrently, the cam pin 13b is moved along the second cam groove 12b of the cam ring 12 and the guide groove 16b of the straight-forward guide ring 16 with the result that the second group lens frame 13 is moved forward as shown by an arrow mark C. With the operation as described above, the first group lens frame 10 and second group lens frame 13 are situated in the optically wide position.
In operation from the wide position to the telephoto position in FIG. 5C, the cam ring 12 is also driven by the gear unit 14; however, because the cam pin 12d moves along a horizontal cam groove 15b of the cam groove 15a in this range, the cam ring 12 does not move in the direction of the optical axis, so that also the straight-forward guide ring 16 does not move in the direction of the optical axis as shown by an arrow mark D. At this moment, the cam pin 10a is moved along the cam groove 12a of the cam ring 12 and the guide groove 16a of the straight-forward guide ring 16 with the result that the first group lens frame 10 is moved in the direction of an arrow mark E.
At the same time, the cam pin 13b is moved along the cam groove 12b of the cam ring 12 and the guide groove 16b of the straight-forward guide ring 16 with the result that the second group lens frame 13 is moved forward in the direction of an arrow mark F. With the operation as described above, the first group lens frame 10 and second group lens frame 13 optically move between the wide position and telephoto position to perform the zooming operation.
In addition, operation from the telephoto position to wide position and operation from the wide position to collapsed state are performed by driving the gear 14a of the gear unit 14 to oppositely rotate and making the cam ring 12 rotate in the opposite direction.
Hereupon, while the first group lens frame 10 and second group lens frame 13 perform the zooming operation, the third group lens frame 18 is displaced minutely in the direction of the optical axis by a separate driving source, not shown, such as a stepping motor to perform focusing operation.
In this way, the image-pickup lens portion 2 makes the first group lens frame 10 and second group lens frame 13 move depending on the position of a subject to selectively perform the zooming operation and focusing operation, so that it is necessary for the image-pickup lens portion 2 to be provided with means for detecting a position of the lens.
As for a conventional zoom position detecting method of the collapsible type lens, for example, a method of detecting the position by a rotation angle of the cam ring and a method of detecting the position by a position of the cam ring in the moving direction are known.
Further, as to the method of detecting position by the rotation angle of cam ring, a method of detecting position by a change in conduction of an electric pattern arranged on an exterior portion of the cam ring, a method of detecting the zoom position, in which a projection for detecting a rotary position and a switch arranged outside thereof are provided on the exterior portion of the cam ring and the switch is operated by the projection, and the like are known.
FIG. 7 shows the former method of detecting a rotary position by an electric contact (brush). In FIG. 7, a reference numeral 50 denotes the image-pickup lens portion of the collapsible type lens, which is designed to be able to take selectively the collapsed position, that is, a retracted state of the lens when not being used, the wide angle position, and the telephoto position. A finder lens 51 is arranged at the upper left of the image-pickup lens portion 50.
A rotary-position detecting means 52 using an electric contact is provided at the top of the image-pickup lens portion 50. The rotary-position detecting means 52 includes an electric contact pattern 53 provided on a rotary part of the lens barrel and a brush portion 54 mounted on a fixed part of the camera body or the like, and a plurality of brushes 55 provided at the brush portion 54 are in slidable contact with the electric contact pattern 53.
Thus, a position of contact of the plurality of brushes 55 with the electric contact pattern 53 varies according to a rotary position of the rotary part of the lens barrel, so that an electric output will be varied depending on the rotary position. By monitoring a change in the electric output, it is possible to detect the zoom position of the lens by the rotary-position detecting means 52.
FIG. 8 shows the latter method of detecting a rotary position by a variable resistor. In FIG. 8, a reference numeral 60 denotes the image-pickup lens portion of a collapsible type lens, which is designed to be able to take selectively the collapsed position, the wide angle position, and the telephoto position as well. A finder lens 61 is arranged at the upper left of the image-pickup lens portion 60 and a rotary-position detecting means 62 using the variable resistor is provided at the lower left of the image-pickup lens portion 60 under the finder lens.
The rotary-position detecting means 62 includes a variable resistor 63 fitted to a fixed part of the camera body or the like, a support member 64 for supporting a detection piece 63a of the variable resistor 63, a lead screw 65 for moving the support member 64 in the direction of an optical axis of the image-pickup lens portion 60, and a gear train 66 which is engaged with a gear portion provided on a rotary part of the lens barrel to transmit the rotational force thereof to the lead screw 65. The gear train 66 includes a driving gear engaged with the gear portion of lens barrel, a screw gear fixed to the lead screw 65, and an idler gear connecting the screw gear and the driving gear to transmit motive power.
Thus, depending on the rotary position of a rotary part of the lens barrel, a resistance value of the variable resistor 63 will change. By monitoring the resistance value output from the variable resistor 63, it is possible to detect the zoom position of the lens by the rotary-position detecting means 62.
As an optical apparatus using the above-described position detecting method, there is also, for example, the one disclosed in Patent Literature 1. The optical apparatus described in the Patent Literature 1 is characterized by including a first lens unit constituting an optical system, a first motor for driving the first lens unit, a second lens unit constituting the optical system, which is provided behind the first lens unit, and a control means for controlling the first and second motors to retract the second lens unit in response to retract instructions of the optical system, to start retracting the first lens unit after the second lens unit has been retracted, and to retract the first lens unit into a space made by retracting the second lens unit.
This optical apparatus is provided with a linear sensor for detecting a lens position, which is fixed to a base by means of a screw and the like. The linear sensor is composed of a variable resistor that generates an output between terminals which linearly changes with its slider moves while a predetermined voltage is applied between the terminals.
Patent Literature 1
Japanese Published Patent Application No. 2000-194046 (page 5, FIG. 12, etc.) However, when among the above described lens position detecting methods the former lens position detecting method according to a rotation angle of the cam ring is employed, it is necessary to arrange a projection, a switch or an electric pattern and the like on an exterior portion of the cam ring, with the result that the exterior portion becomes large in size and also the number of parts as well as the number of processes increase, which causes the problem of not being economical.
When using the latter position detecting method according to a position of the cam ring in its protruding direction, it is necessary to provide a projection on the exterior portion and also to provide a switch or a leaf spring at a predetermined position corresponding to the projection, with the result that, although the number of parts increases less than that in the former method, the exterior portion becomes bulky and against the miniaturization, which poses another problem.
Furthermore, when employing either of the position detecting methods, there exists a sliding portion such as a mechanical switch or brushes for detecting the conduction, so that a load against the lens will occur due to a frictional resistance of the sliding portion. For this reason, there is also posed a problem that movement efficiency of the lens to the driving force will deteriorate.
The present invention has been made to solve the above-described problems and provides an optical unit in which a position detecting means is provided inside the movable lens barrel and the position is detected within the lens barrel, thereby miniaturizing the whole apparatus and also preventing a collision between lens portions arranged in the lens barrel, as well as an image-pickup apparatus including the optical unit.